ocfs2: temporarily remove extent map caching

The code in extent_map.c is not prepared to deal with a subtree being
rotated between lookups. This can happen when filling holes in sparse files.
Instead of a lengthy patch to update the code (which would likely lose the
benefit of caching subtree roots), we remove most of the algorithms and
implement a simple path based lookup. A less ambitious extent caching scheme
will be added in a later patch.

Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>

1 files changed, 81 insertions, 943 deletions

diff --git a/fs/ocfs2/extent_map.c b/fs/ocfs2/extent_map.c
index 80ac69f11d9f..3b4322fd369a 100644
--- a/fs/ocfs2/extent_map.c
+++ b/fs/ocfs2/extent_map.c
@@ -3,8 +3,7 @@
  *
  * extent_map.c
  *
- * In-memory extent map for OCFS2.  Man, this code was prettier in
- * the library.
+ * Block/Cluster mapping functions
  *
  * Copyright (C) 2004 Oracle.  All rights reserved.
  *
@@ -26,1016 +25,155 @@
 #include <linux/fs.h>
 #include <linux/init.h>
 #include <linux/types.h>
-#include <linux/slab.h>
-#include <linux/rbtree.h>
 
 #define MLOG_MASK_PREFIX ML_EXTENT_MAP
 #include <cluster/masklog.h>
 
 #include "ocfs2.h"
 
+#include "alloc.h"
 #include "extent_map.h"
 #include "inode.h"
 #include "super.h"
 
 #include "buffer_head_io.h"
 
-
-/*
- * SUCK SUCK SUCK
- * Our headers are so bad that struct ocfs2_extent_map is in ocfs.h
- */
-
-struct ocfs2_extent_map_entry {
-	struct rb_node e_node;
-	int e_tree_depth;
-	struct ocfs2_extent_rec e_rec;
-};
-
-struct ocfs2_em_insert_context {
-	int need_left;
-	int need_right;
-	struct ocfs2_extent_map_entry *new_ent;
-	struct ocfs2_extent_map_entry *old_ent;
-	struct ocfs2_extent_map_entry *left_ent;
-	struct ocfs2_extent_map_entry *right_ent;
-};
-
-static struct kmem_cache *ocfs2_em_ent_cachep = NULL;
-
-
-static struct ocfs2_extent_map_entry *
-ocfs2_extent_map_lookup(struct ocfs2_extent_map *em,
-			u32 cpos, u32 clusters,
-			struct rb_node ***ret_p,
-			struct rb_node **ret_parent);
-static int ocfs2_extent_map_insert(struct inode *inode,
-				   struct ocfs2_extent_rec *rec,
-				   int tree_depth);
-static int ocfs2_extent_map_insert_entry(struct ocfs2_extent_map *em,
-					 struct ocfs2_extent_map_entry *ent);
-static int ocfs2_extent_map_find_leaf(struct inode *inode,
-				      u32 cpos, u32 clusters,
-				      struct ocfs2_extent_list *el);
-static int ocfs2_extent_map_lookup_read(struct inode *inode,
-					u32 cpos, u32 clusters,
-					struct ocfs2_extent_map_entry **ret_ent);
-static int ocfs2_extent_map_try_insert(struct inode *inode,
-				       struct ocfs2_extent_rec *rec,
-				       int tree_depth,
-				       struct ocfs2_em_insert_context *ctxt);
-
-/* returns 1 only if the rec contains all the given clusters -- that is that
- * rec's cpos is <= the cluster cpos and that the rec endpoint (cpos +
- * clusters) is >= the argument's endpoint */
-static int ocfs2_extent_rec_contains_clusters(struct ocfs2_extent_rec *rec,
-					      u32 cpos, u32 clusters)
-{
-	if (le32_to_cpu(rec->e_cpos) > cpos)
-		return 0;
-	if (cpos + clusters > le32_to_cpu(rec->e_cpos) + 
-			      le32_to_cpu(rec->e_clusters))
-		return 0;
-	return 1;
-}
-
-
 /*
- * Find an entry in the tree that intersects the region passed in.
- * Note that this will find straddled intervals, it is up to the
- * callers to enforce any boundary conditions.
- *
- * Callers must hold ip_lock.  This lookup is not guaranteed to return
- * a tree_depth 0 match, and as such can race inserts if the lock
- * were not held.
+ * Return the index of the extent record which contains cluster #v_cluster.
+ * -1 is returned if it was not found.
  *
- * The rb_node garbage lets insertion share the search.  Trivial
- * callers pass NULL.
+ * Should work fine on interior and exterior nodes.
  */
-static struct ocfs2_extent_map_entry *
-ocfs2_extent_map_lookup(struct ocfs2_extent_map *em,
-			u32 cpos, u32 clusters,
-			struct rb_node ***ret_p,
-			struct rb_node **ret_parent)
+static int ocfs2_search_extent_list(struct ocfs2_extent_list *el,
+				    u32 v_cluster)
 {
-	struct rb_node **p = &em->em_extents.rb_node;
-	struct rb_node *parent = NULL;
-	struct ocfs2_extent_map_entry *ent = NULL;
-
-	while (*p)
-	{
-		parent = *p;
-		ent = rb_entry(parent, struct ocfs2_extent_map_entry,
-			       e_node);
-		if ((cpos + clusters) <= le32_to_cpu(ent->e_rec.e_cpos)) {
-			p = &(*p)->rb_left;
-			ent = NULL;
-		} else if (cpos >= (le32_to_cpu(ent->e_rec.e_cpos) +
-				    le32_to_cpu(ent->e_rec.e_clusters))) {
-			p = &(*p)->rb_right;
-			ent = NULL;
-		} else
-			break;
-	}
-
-	if (ret_p != NULL)
-		*ret_p = p;
-	if (ret_parent != NULL)
-		*ret_parent = parent;
-	return ent;
-}
-
-/*
- * Find the leaf containing the interval we want.  While we're on our
- * way down the tree, fill in every record we see at any depth, because
- * we might want it later.
- *
- * Note that this code is run without ip_lock.  That's because it
- * sleeps while reading.  If someone is also filling the extent list at
- * the same time we are, we might have to restart.
- */
-static int ocfs2_extent_map_find_leaf(struct inode *inode,
-				      u32 cpos, u32 clusters,
-				      struct ocfs2_extent_list *el)
-{
-	int i, ret;
-	struct buffer_head *eb_bh = NULL;
-	u64 blkno;
-	u32 rec_end;
-	struct ocfs2_extent_block *eb;
+	int ret = -1;
+	int i;
 	struct ocfs2_extent_rec *rec;
+	u32 rec_end, rec_start;
 
-	/*
-	 * The bh data containing the el cannot change here, because
-	 * we hold alloc_sem.  So we can do this without other
-	 * locks.
-	 */
-	while (el->l_tree_depth)
-	{
-		blkno = 0;
-		for (i = 0; i < le16_to_cpu(el->l_next_free_rec); i++) {
-			rec = &el->l_recs[i];
-			rec_end = (le32_to_cpu(rec->e_cpos) +
-				   le32_to_cpu(rec->e_clusters));
-
-			ret = -EBADR;
-			if (rec_end > OCFS2_I(inode)->ip_clusters) {
-				mlog_errno(ret);
-				ocfs2_error(inode->i_sb,
-					    "Extent %d at e_blkno %llu of inode %llu goes past ip_clusters of %u\n",
-					    i,
-					    (unsigned long long)le64_to_cpu(rec->e_blkno),
-					    (unsigned long long)OCFS2_I(inode)->ip_blkno,
-					    OCFS2_I(inode)->ip_clusters);
-				goto out_free;
-			}
-
-			if (rec_end <= cpos) {
-				ret = ocfs2_extent_map_insert(inode, rec,
-						le16_to_cpu(el->l_tree_depth));
-				if (ret && (ret != -EEXIST)) {
-					mlog_errno(ret);
-					goto out_free;
-				}
-				continue;
-			}
-			if ((cpos + clusters) <= le32_to_cpu(rec->e_cpos)) {
-				ret = ocfs2_extent_map_insert(inode, rec,
-						le16_to_cpu(el->l_tree_depth));
-				if (ret && (ret != -EEXIST)) {
-					mlog_errno(ret);
-					goto out_free;
-				}
-				continue;
-			}
-
-			/*
-			 * We've found a record that matches our
-			 * interval.  We don't insert it because we're
-			 * about to traverse it.
-			 */
-
-			/* Check to see if we're stradling */
-			ret = -ESRCH;
-			if (!ocfs2_extent_rec_contains_clusters(rec,
-							        cpos,
-								clusters)) {
-				mlog_errno(ret);
-				goto out_free;
-			}
-
-			/*
-			 * If we've already found a record, the el has
-			 * two records covering the same interval.
-			 * EEEK!
-			 */
-			ret = -EBADR;
-			if (blkno) {
-				mlog_errno(ret);
-				ocfs2_error(inode->i_sb,
-					    "Multiple extents for (cpos = %u, clusters = %u) on inode %llu; e_blkno %llu and rec %d at e_blkno %llu\n",
-					    cpos, clusters,
-					    (unsigned long long)OCFS2_I(inode)->ip_blkno,
-					    (unsigned long long)blkno, i,
-					    (unsigned long long)le64_to_cpu(rec->e_blkno));
-				goto out_free;
-			}
-
-			blkno = le64_to_cpu(rec->e_blkno);
-		}
-
-		/*
-		 * We don't support holes, and we're still up
-		 * in the branches, so we'd better have found someone
-		 */
-		ret = -EBADR;
-		if (!blkno) {
-			ocfs2_error(inode->i_sb,
-				    "No record found for (cpos = %u, clusters = %u) on inode %llu\n",
-				    cpos, clusters,
-				    (unsigned long long)OCFS2_I(inode)->ip_blkno);
-			mlog_errno(ret);
-			goto out_free;
-		}
-
-		if (eb_bh) {
-			brelse(eb_bh);
-			eb_bh = NULL;
-		}
-		ret = ocfs2_read_block(OCFS2_SB(inode->i_sb),
-				       blkno, &eb_bh, OCFS2_BH_CACHED,
-				       inode);
-		if (ret) {
-			mlog_errno(ret);
-			goto out_free;
-		}
-		eb = (struct ocfs2_extent_block *)eb_bh->b_data;
-		if (!OCFS2_IS_VALID_EXTENT_BLOCK(eb)) {
-			OCFS2_RO_ON_INVALID_EXTENT_BLOCK(inode->i_sb, eb);
-			ret = -EIO;
-			goto out_free;
-		}
-		el = &eb->h_list;
-	}
-
-	BUG_ON(el->l_tree_depth);
-
-	for (i = 0; i < le16_to_cpu(el->l_next_free_rec); i++) {
+	for(i = 0; i < le16_to_cpu(el->l_next_free_rec); i++) {
 		rec = &el->l_recs[i];
 
-		if ((le32_to_cpu(rec->e_cpos) + le32_to_cpu(rec->e_clusters)) >
-		    OCFS2_I(inode)->ip_clusters) {
-			ret = -EBADR;
-			mlog_errno(ret);
-			ocfs2_error(inode->i_sb,
-				    "Extent %d at e_blkno %llu of inode %llu goes past ip_clusters of %u\n",
-				    i,
-				    (unsigned long long)le64_to_cpu(rec->e_blkno),
-				    (unsigned long long)OCFS2_I(inode)->ip_blkno,
-				    OCFS2_I(inode)->ip_clusters);
-			return ret;
-		}
+		rec_start = le32_to_cpu(rec->e_cpos);
+		rec_end = rec_start + le32_to_cpu(rec->e_clusters);
 
-		ret = ocfs2_extent_map_insert(inode, rec,
-					      le16_to_cpu(el->l_tree_depth));
-		if (ret && (ret != -EEXIST)) {
-			mlog_errno(ret);
-			goto out_free;
+		if (v_cluster >= rec_start && v_cluster < rec_end) {
+			ret = i;
+			break;
 		}
 	}
 
-	ret = 0;
-
-out_free:
-	if (eb_bh)
-		brelse(eb_bh);
-
 	return ret;
 }
 
-/*
- * This lookup actually will read from disk.  It has one invariant:
- * It will never re-traverse blocks.  This means that all inserts should
- * be new regions or more granular regions (both allowed by insert).
- */
-static int ocfs2_extent_map_lookup_read(struct inode *inode,
-					u32 cpos,
-					u32 clusters,
-					struct ocfs2_extent_map_entry **ret_ent)
+static int ocfs2_get_clusters(struct inode *inode, u32 v_cluster,
+			      u32 *p_cluster, u32 *num_clusters)
 {
-	int ret;
-	u64 blkno;
-	struct ocfs2_extent_map *em = &OCFS2_I(inode)->ip_map;
-	struct ocfs2_extent_map_entry *ent;
-	struct buffer_head *bh = NULL;
-	struct ocfs2_extent_block *eb;
+	int ret, i;
+	struct buffer_head *di_bh = NULL;
+	struct buffer_head *eb_bh = NULL;
 	struct ocfs2_dinode *di;
+	struct ocfs2_extent_block *eb;
 	struct ocfs2_extent_list *el;
+	struct ocfs2_extent_rec *rec;
+	u32 coff;
 
-	spin_lock(&OCFS2_I(inode)->ip_lock);
-	ent = ocfs2_extent_map_lookup(em, cpos, clusters, NULL, NULL);
-	if (ent) {
-		if (!ent->e_tree_depth) {
-			spin_unlock(&OCFS2_I(inode)->ip_lock);
-			*ret_ent = ent;
-			return 0;
-		}
-		blkno = le64_to_cpu(ent->e_rec.e_blkno);
-		spin_unlock(&OCFS2_I(inode)->ip_lock);
-
-		ret = ocfs2_read_block(OCFS2_SB(inode->i_sb), blkno, &bh,
-				       OCFS2_BH_CACHED, inode);
-		if (ret) {
-			mlog_errno(ret);
-			if (bh)
-				brelse(bh);
-			return ret;
-		}
-		eb = (struct ocfs2_extent_block *)bh->b_data;
-		if (!OCFS2_IS_VALID_EXTENT_BLOCK(eb)) {
-			OCFS2_RO_ON_INVALID_EXTENT_BLOCK(inode->i_sb, eb);
-			brelse(bh);
-			return -EIO;
-		}
-		el = &eb->h_list;
-	} else {
-		spin_unlock(&OCFS2_I(inode)->ip_lock);
-
-		ret = ocfs2_read_block(OCFS2_SB(inode->i_sb),
-				       OCFS2_I(inode)->ip_blkno, &bh,
-				       OCFS2_BH_CACHED, inode);
-		if (ret) {
-			mlog_errno(ret);
-			if (bh)
-				brelse(bh);
-			return ret;
-		}
-		di = (struct ocfs2_dinode *)bh->b_data;
-		if (!OCFS2_IS_VALID_DINODE(di)) {
-			brelse(bh);
-			OCFS2_RO_ON_INVALID_DINODE(inode->i_sb, di);
-			return -EIO;
-		}
-		el = &di->id2.i_list;
-	}
-
-	ret = ocfs2_extent_map_find_leaf(inode, cpos, clusters, el);
-	brelse(bh);
+	ret = ocfs2_read_block(OCFS2_SB(inode->i_sb), OCFS2_I(inode)->ip_blkno,
+			       &di_bh, OCFS2_BH_CACHED, inode);
 	if (ret) {
 		mlog_errno(ret);
-		return ret;
+		goto out;
 	}
 
-	ent = ocfs2_extent_map_lookup(em, cpos, clusters, NULL, NULL);
-	if (!ent) {
-		ret = -ESRCH;
-		mlog_errno(ret);
-		return ret;
-	}
-
-	/* FIXME: Make sure this isn't a corruption */
-	BUG_ON(ent->e_tree_depth);
+	di = (struct ocfs2_dinode *) di_bh->b_data;
+	el = &di->id2.i_list;
 
-	*ret_ent = ent;
-
-	return 0;
-}
-
-/*
- * Callers must hold ip_lock.  This can insert pieces of the tree,
- * thus racing lookup if the lock weren't held.
- */
-static int ocfs2_extent_map_insert_entry(struct ocfs2_extent_map *em,
-					 struct ocfs2_extent_map_entry *ent)
-{
-	struct rb_node **p, *parent;
-	struct ocfs2_extent_map_entry *old_ent;
-
-	old_ent = ocfs2_extent_map_lookup(em, le32_to_cpu(ent->e_rec.e_cpos),
-					  le32_to_cpu(ent->e_rec.e_clusters),
-					  &p, &parent);
-	if (old_ent)
-		return -EEXIST;
-
-	rb_link_node(&ent->e_node, parent, p);
-	rb_insert_color(&ent->e_node, &em->em_extents);
-
-	return 0;
-}
-
-
-/*
- * Simple rule: on any return code other than -EAGAIN, anything left
- * in the insert_context will be freed.
- *
- * Simple rule #2: A return code of -EEXIST from this function or
- * its calls to ocfs2_extent_map_insert_entry() signifies that another
- * thread beat us to the insert.  It is not an actual error, but it
- * tells the caller we have no more work to do.
- */
-static int ocfs2_extent_map_try_insert(struct inode *inode,
-				       struct ocfs2_extent_rec *rec,
-				       int tree_depth,
-				       struct ocfs2_em_insert_context *ctxt)
-{
-	int ret;
-	struct ocfs2_extent_map *em = &OCFS2_I(inode)->ip_map;
-	struct ocfs2_extent_map_entry *old_ent;
-
-	ctxt->need_left = 0;
-	ctxt->need_right = 0;
-	ctxt->old_ent = NULL;
-
-	spin_lock(&OCFS2_I(inode)->ip_lock);
-	ret = ocfs2_extent_map_insert_entry(em, ctxt->new_ent);
-	if (!ret) {
-		ctxt->new_ent = NULL;
-		goto out_unlock;
-	}
-
-	/* Since insert_entry failed, the map MUST have old_ent */
-	old_ent = ocfs2_extent_map_lookup(em, le32_to_cpu(rec->e_cpos),
-					  le32_to_cpu(rec->e_clusters),
-					  NULL, NULL);
-
-	BUG_ON(!old_ent);
+	if (el->l_tree_depth) {
+		ret = ocfs2_find_leaf(inode, el, v_cluster, &eb_bh);
+		if (ret) {
+			mlog_errno(ret);
+			goto out;
+		}
 
-	if (old_ent->e_tree_depth < tree_depth) {
-		/* Another thread beat us to the lower tree_depth */
-		ret = -EEXIST;
-		goto out_unlock;
+		eb = (struct ocfs2_extent_block *) eb_bh->b_data;
+		el = &eb->h_list;
 	}
 
-	if (old_ent->e_tree_depth == tree_depth) {
+	i = ocfs2_search_extent_list(el, v_cluster);
+	if (i == -1) {
 		/*
-		 * Another thread beat us to this tree_depth.
-		 * Let's make sure we agree with that thread (the
-		 * extent_rec should be identical).
+		 * A hole was found. Return some canned values that
+		 * callers can key on.
 		 */
-		if (!memcmp(rec, &old_ent->e_rec,
-			    sizeof(struct ocfs2_extent_rec)))
-			ret = 0;
-		else
-			/* FIXME: Should this be ESRCH/EBADR??? */
-			ret = -EEXIST;
+		*p_cluster = 0;
+		if (num_clusters)
+			*num_clusters = 1;
+	} else {
+		rec = &el->l_recs[i];
 
-		goto out_unlock;
-	}
+		BUG_ON(v_cluster < le32_to_cpu(rec->e_cpos));
 
-	/*
-	 * We do it in this order specifically so that no actual tree
-	 * changes occur until we have all the pieces we need.  We
-	 * don't want malloc failures to leave an inconsistent tree.
-	 * Whenever we drop the lock, another process could be
-	 * inserting.  Also note that, if another process just beat us
-	 * to an insert, we might not need the same pieces we needed
-	 * the first go round.  In the end, the pieces we need will
-	 * be used, and the pieces we don't will be freed.
-	 */
-	ctxt->need_left = !!(le32_to_cpu(rec->e_cpos) >
-			     le32_to_cpu(old_ent->e_rec.e_cpos));
-	ctxt->need_right = !!((le32_to_cpu(old_ent->e_rec.e_cpos) +
-			       le32_to_cpu(old_ent->e_rec.e_clusters)) >
-			      (le32_to_cpu(rec->e_cpos) + le32_to_cpu(rec->e_clusters)));
-	ret = -EAGAIN;
-	if (ctxt->need_left) {
-		if (!ctxt->left_ent)
-			goto out_unlock;
-		*(ctxt->left_ent) = *old_ent;
-		ctxt->left_ent->e_rec.e_clusters =
-			cpu_to_le32(le32_to_cpu(rec->e_cpos) -
-				    le32_to_cpu(ctxt->left_ent->e_rec.e_cpos));
-	}
-	if (ctxt->need_right) {
-		if (!ctxt->right_ent)
-			goto out_unlock;
-		*(ctxt->right_ent) = *old_ent;
-		ctxt->right_ent->e_rec.e_cpos =
-			cpu_to_le32(le32_to_cpu(rec->e_cpos) +
+		if (!rec->e_blkno) {
+			ocfs2_error(inode->i_sb, "Inode %lu has bad extent "
+				    "record (%u, %u, 0)", inode->i_ino,
+				    le32_to_cpu(rec->e_cpos),
 				    le32_to_cpu(rec->e_clusters));
-		ctxt->right_ent->e_rec.e_clusters =
-			cpu_to_le32((le32_to_cpu(old_ent->e_rec.e_cpos) +
-				     le32_to_cpu(old_ent->e_rec.e_clusters)) -
-				    le32_to_cpu(ctxt->right_ent->e_rec.e_cpos));
-	}
-
-	rb_erase(&old_ent->e_node, &em->em_extents);
-	/* Now that he's erased, set him up for deletion */
-	ctxt->old_ent = old_ent;
-
-	if (ctxt->need_left) {
-		ret = ocfs2_extent_map_insert_entry(em,
-						    ctxt->left_ent);
-		if (ret)
-			goto out_unlock;
-		ctxt->left_ent = NULL;
-	}
-
-	if (ctxt->need_right) {
-		ret = ocfs2_extent_map_insert_entry(em,
-						    ctxt->right_ent);
-		if (ret)
-			goto out_unlock;
-		ctxt->right_ent = NULL;
-	}
-
-	ret = ocfs2_extent_map_insert_entry(em, ctxt->new_ent);
-
-	if (!ret)
-		ctxt->new_ent = NULL;
-
-out_unlock:
-	spin_unlock(&OCFS2_I(inode)->ip_lock);
-
-	return ret;
-}
-
-
-static int ocfs2_extent_map_insert(struct inode *inode,
-				   struct ocfs2_extent_rec *rec,
-				   int tree_depth)
-{
-	int ret;
-	struct ocfs2_em_insert_context ctxt = {0, };
-
-	if ((le32_to_cpu(rec->e_cpos) + le32_to_cpu(rec->e_clusters)) >
-	    OCFS2_I(inode)->ip_map.em_clusters) {
-		ret = -EBADR;
-		mlog_errno(ret);
-		return ret;
-	}
-
-	/* Zero e_clusters means a truncated tail record.  It better be EOF */
-	if (!rec->e_clusters) {
-		if ((le32_to_cpu(rec->e_cpos) + le32_to_cpu(rec->e_clusters)) !=
-		    OCFS2_I(inode)->ip_map.em_clusters) {
-			ret = -EBADR;
-			mlog_errno(ret);
-			ocfs2_error(inode->i_sb,
-				    "Zero e_clusters on non-tail extent record at e_blkno %llu on inode %llu\n",
-				    (unsigned long long)le64_to_cpu(rec->e_blkno),
-				    (unsigned long long)OCFS2_I(inode)->ip_blkno);
-			return ret;
-		}
-
-		/* Ignore the truncated tail */
-		return 0;
-	}
-
-	ret = -ENOMEM;
-	ctxt.new_ent = kmem_cache_alloc(ocfs2_em_ent_cachep,
-					GFP_NOFS);
-	if (!ctxt.new_ent) {
-		mlog_errno(ret);
-		return ret;
-	}
-
-	ctxt.new_ent->e_rec = *rec;
-	ctxt.new_ent->e_tree_depth = tree_depth;
-
-	do {
-		ret = -ENOMEM;
-		if (ctxt.need_left && !ctxt.left_ent) {
-			ctxt.left_ent =
-				kmem_cache_alloc(ocfs2_em_ent_cachep,
-						 GFP_NOFS);
-			if (!ctxt.left_ent)
-				break;
-		}
-		if (ctxt.need_right && !ctxt.right_ent) {
-			ctxt.right_ent =
-				kmem_cache_alloc(ocfs2_em_ent_cachep,
-						 GFP_NOFS);
-			if (!ctxt.right_ent)
-				break;
+			ret = -EROFS;
+			goto out;
 		}
 
-		ret = ocfs2_extent_map_try_insert(inode, rec,
-						  tree_depth, &ctxt);
-	} while (ret == -EAGAIN);
+		coff = v_cluster - le32_to_cpu(rec->e_cpos);
 
-	if ((ret < 0) && (ret != -EEXIST))
-		mlog_errno(ret);
-
-	if (ctxt.left_ent)
-		kmem_cache_free(ocfs2_em_ent_cachep, ctxt.left_ent);
-	if (ctxt.right_ent)
-		kmem_cache_free(ocfs2_em_ent_cachep, ctxt.right_ent);
-	if (ctxt.old_ent)
-		kmem_cache_free(ocfs2_em_ent_cachep, ctxt.old_ent);
-	if (ctxt.new_ent)
-		kmem_cache_free(ocfs2_em_ent_cachep, ctxt.new_ent);
-
-	return ret;
-}
+		*p_cluster = ocfs2_blocks_to_clusters(inode->i_sb,
+						    le64_to_cpu(rec->e_blkno));
+		*p_cluster = *p_cluster + coff;
 
-/*
- * Append this record to the tail of the extent map.  It must be
- * tree_depth 0.  The record might be an extension of an existing
- * record, and as such that needs to be handled.  eg:
- *
- * Existing record in the extent map:
- *
- *	cpos = 10, len = 10
- *	|---------|
- *
- * New Record:
- *
- *	cpos = 10, len = 20
- *	|------------------|
- *
- * The passed record is the new on-disk record.  The new_clusters value
- * is how many clusters were added to the file.  If the append is a
- * contiguous append, the new_clusters has been added to
- * rec->e_clusters.  If the append is an entirely new extent, then
- * rec->e_clusters is == new_clusters.
- */
-int ocfs2_extent_map_append(struct inode *inode,
-			    struct ocfs2_extent_rec *rec,
-			    u32 new_clusters)
-{
-	int ret;
-	struct ocfs2_extent_map *em = &OCFS2_I(inode)->ip_map;
-	struct ocfs2_extent_map_entry *ent;
-	struct ocfs2_extent_rec *old;
-
-	BUG_ON(!new_clusters);
-	BUG_ON(le32_to_cpu(rec->e_clusters) < new_clusters);
-
-	if (em->em_clusters < OCFS2_I(inode)->ip_clusters) {
-		/*
-		 * Size changed underneath us on disk.  Drop any
-		 * straddling records and update our idea of
-		 * i_clusters
-		 */
-		ocfs2_extent_map_drop(inode, em->em_clusters - 1);
-		em->em_clusters = OCFS2_I(inode)->ip_clusters;
+		if (num_clusters)
+			*num_clusters = le32_to_cpu(rec->e_clusters) - coff;
 	}
 
-	mlog_bug_on_msg((le32_to_cpu(rec->e_cpos) +
-			 le32_to_cpu(rec->e_clusters)) !=
-			(em->em_clusters + new_clusters),
-			"Inode %llu:\n"
-			"rec->e_cpos = %u + rec->e_clusters = %u = %u\n"
-			"em->em_clusters = %u + new_clusters = %u = %u\n",
-			(unsigned long long)OCFS2_I(inode)->ip_blkno,
-			le32_to_cpu(rec->e_cpos), le32_to_cpu(rec->e_clusters),
-			le32_to_cpu(rec->e_cpos) + le32_to_cpu(rec->e_clusters),
-			em->em_clusters, new_clusters,
-			em->em_clusters + new_clusters);
-
-	em->em_clusters += new_clusters;
-
-	ret = -ENOENT;
-	if (le32_to_cpu(rec->e_clusters) > new_clusters) {
-		/* This is a contiguous append */
-		ent = ocfs2_extent_map_lookup(em, le32_to_cpu(rec->e_cpos), 1,
-					      NULL, NULL);
-		if (ent) {
-			old = &ent->e_rec;
-			BUG_ON((le32_to_cpu(rec->e_cpos) +
-				le32_to_cpu(rec->e_clusters)) !=
-				 (le32_to_cpu(old->e_cpos) +
-				  le32_to_cpu(old->e_clusters) +
-				  new_clusters));
-			if (ent->e_tree_depth == 0) {
-				BUG_ON(le32_to_cpu(old->e_cpos) !=
-				       le32_to_cpu(rec->e_cpos));
-				BUG_ON(le64_to_cpu(old->e_blkno) !=
-				       le64_to_cpu(rec->e_blkno));
-				ret = 0;
-			}
-			/*
-			 * Let non-leafs fall through as -ENOENT to
-			 * force insertion of the new leaf.
-			 */
-			le32_add_cpu(&old->e_clusters, new_clusters);
-		}
-	}
-
-	if (ret == -ENOENT)
-		ret = ocfs2_extent_map_insert(inode, rec, 0);
-	if (ret < 0)
-		mlog_errno(ret);
+out:
+	brelse(di_bh);
+	brelse(eb_bh);
 	return ret;
 }
 
-#if 0
-/* Code here is included but defined out as it completes the extent
- * map api and may be used in the future. */
-
 /*
- * Look up the record containing this cluster offset.  This record is
- * part of the extent map.  Do not free it.  Any changes you make to
- * it will reflect in the extent map.  So, if your last extent
- * is (cpos = 10, clusters = 10) and you truncate the file by 5
- * clusters, you can do:
- *
- * ret = ocfs2_extent_map_get_rec(em, orig_size - 5, &rec);
- * rec->e_clusters -= 5;
- *
- * The lookup does not read from disk.  If the map isn't filled in for
- * an entry, you won't find it.
- *
- * Also note that the returned record is valid until alloc_sem is
- * dropped.  After that, truncate and extend can happen.  Caveat Emptor.
+ * This expects alloc_sem to be held. The allocation cannot change at
+ * all while the map is in the process of being updated.
  */
-int ocfs2_extent_map_get_rec(struct inode *inode, u32 cpos,
-			     struct ocfs2_extent_rec **rec,
-			     int *tree_depth)
-{
-	int ret = -ENOENT;
-	struct ocfs2_extent_map *em = &OCFS2_I(inode)->ip_map;
-	struct ocfs2_extent_map_entry *ent;
-
-	*rec = NULL;
-
-	if (cpos >= OCFS2_I(inode)->ip_clusters)
-		return -EINVAL;
-
-	if (cpos >= em->em_clusters) {
-		/*
-		 * Size changed underneath us on disk.  Drop any
-		 * straddling records and update our idea of
-		 * i_clusters
-		 */
-		ocfs2_extent_map_drop(inode, em->em_clusters - 1);
-		em->em_clusters = OCFS2_I(inode)->ip_clusters ;
-	}
-
-	ent = ocfs2_extent_map_lookup(&OCFS2_I(inode)->ip_map, cpos, 1,
-				      NULL, NULL);
-
-	if (ent) {
-		*rec = &ent->e_rec;
-		if (tree_depth)
-			*tree_depth = ent->e_tree_depth;
-		ret = 0;
-	}
-
-	return ret;
-}
-
-int ocfs2_extent_map_get_clusters(struct inode *inode,
-				  u32 v_cpos, int count,
-				  u32 *p_cpos, int *ret_count)
-{
-	int ret;
-	u32 coff, ccount;
-	struct ocfs2_extent_map *em = &OCFS2_I(inode)->ip_map;
-	struct ocfs2_extent_map_entry *ent = NULL;
-
-	*p_cpos = ccount = 0;
-
-	if ((v_cpos + count) > OCFS2_I(inode)->ip_clusters)
-		return -EINVAL;
-
-	if ((v_cpos + count) > em->em_clusters) {
-		/*
-		 * Size changed underneath us on disk.  Drop any
-		 * straddling records and update our idea of
-		 * i_clusters
-		 */
-		ocfs2_extent_map_drop(inode, em->em_clusters - 1);
-		em->em_clusters = OCFS2_I(inode)->ip_clusters;
-	}
-
-
-	ret = ocfs2_extent_map_lookup_read(inode, v_cpos, count, &ent);
-	if (ret)
-		return ret;
-
-	if (ent) {
-		/* We should never find ourselves straddling an interval */
-		if (!ocfs2_extent_rec_contains_clusters(&ent->e_rec,
-							v_cpos,
-							count))
-			return -ESRCH;
-
-		coff = v_cpos - le32_to_cpu(ent->e_rec.e_cpos);
-		*p_cpos = ocfs2_blocks_to_clusters(inode->i_sb,
-				le64_to_cpu(ent->e_rec.e_blkno)) +
-			  coff;
-
-		if (ret_count)
-			*ret_count = le32_to_cpu(ent->e_rec.e_clusters) - coff;
-
-		return 0;
-	}
-
-
-	return -ENOENT;
-}
-
-#endif  /*  0  */
-
-int ocfs2_extent_map_get_blocks(struct inode *inode,
-				u64 v_blkno, int count,
-				u64 *p_blkno, int *ret_count)
+int ocfs2_extent_map_get_blocks(struct inode *inode, u64 v_blkno, u64 *p_blkno,
+				int *ret_count)
 {
 	int ret;
-	u64 boff;
-	u32 cpos, clusters;
 	int bpc = ocfs2_clusters_to_blocks(inode->i_sb, 1);
-	struct ocfs2_extent_map_entry *ent = NULL;
-	struct ocfs2_extent_map *em = &OCFS2_I(inode)->ip_map;
-	struct ocfs2_extent_rec *rec;
-
-	*p_blkno = 0;
+	u32 cpos, num_clusters, p_cluster;
+	u64 boff = 0;
 
 	cpos = ocfs2_blocks_to_clusters(inode->i_sb, v_blkno);
-	clusters = ocfs2_blocks_to_clusters(inode->i_sb,
-					    (u64)count + bpc - 1);
-	if ((cpos + clusters) > OCFS2_I(inode)->ip_clusters) {
-		ret = -EINVAL;
-		mlog_errno(ret);
-		return ret;
-	}
 
-	if ((cpos + clusters) > em->em_clusters) {
-		/*
-		 * Size changed underneath us on disk.  Drop any
-		 * straddling records and update our idea of
-		 * i_clusters
-		 */
-		ocfs2_extent_map_drop(inode, em->em_clusters - 1);
-		em->em_clusters = OCFS2_I(inode)->ip_clusters;
-	}
-
-	ret = ocfs2_extent_map_lookup_read(inode, cpos, clusters, &ent);
+	ret = ocfs2_get_clusters(inode, cpos, &p_cluster, &num_clusters);
 	if (ret) {
 		mlog_errno(ret);
-		return ret;
+		goto out;
 	}
 
-	if (ent)
-	{
-		rec = &ent->e_rec;
-
-		/* We should never find ourselves straddling an interval */
-		if (!ocfs2_extent_rec_contains_clusters(rec, cpos, clusters)) {
-			ret = -ESRCH;
-			mlog_errno(ret);
-			return ret;
-		}
-
-		boff = ocfs2_clusters_to_blocks(inode->i_sb, cpos -
-						le32_to_cpu(rec->e_cpos));
+	/*
+	 * p_cluster == 0 indicates a hole.
+	 */
+	if (p_cluster) {
+		boff = ocfs2_clusters_to_blocks(inode->i_sb, p_cluster);
 		boff += (v_blkno & (u64)(bpc - 1));
-		*p_blkno = le64_to_cpu(rec->e_blkno) + boff;
-
-		if (ret_count) {
-			*ret_count = ocfs2_clusters_to_blocks(inode->i_sb,
-					le32_to_cpu(rec->e_clusters)) - boff;
-		}
-
-		return 0;
 	}
 
-	return -ENOENT;
-}
-
-int ocfs2_extent_map_init(struct inode *inode)
-{
-	struct ocfs2_extent_map *em = &OCFS2_I(inode)->ip_map;
+	*p_blkno = boff;
 
-	em->em_extents = RB_ROOT;
-	em->em_clusters = 0;
-
-	return 0;
-}
-
-/* Needs the lock */
-static void __ocfs2_extent_map_drop(struct inode *inode,
-				    u32 new_clusters,
-				    struct rb_node **free_head,
-				    struct ocfs2_extent_map_entry **tail_ent)
-{
-	struct rb_node *node, *next;
-	struct ocfs2_extent_map *em = &OCFS2_I(inode)->ip_map;
-	struct ocfs2_extent_map_entry *ent;
-
-	*free_head = NULL;
-
-	ent = NULL;
-	node = rb_last(&em->em_extents);
-	while (node)
-	{
-		next = rb_prev(node);
-
-		ent = rb_entry(node, struct ocfs2_extent_map_entry,
-			       e_node);
-		if (le32_to_cpu(ent->e_rec.e_cpos) < new_clusters)
-			break;
-
-		rb_erase(&ent->e_node, &em->em_extents);
-
-		node->rb_right = *free_head;
-		*free_head = node;
-
-		ent = NULL;
-		node = next;
-	}
-
-	/* Do we have an entry straddling new_clusters? */
-	if (tail_ent) {
-		if (ent &&
-		    ((le32_to_cpu(ent->e_rec.e_cpos) +
-		      le32_to_cpu(ent->e_rec.e_clusters)) > new_clusters))
-			*tail_ent = ent;
-		else
-			*tail_ent = NULL;
+	if (ret_count) {
+		*ret_count = ocfs2_clusters_to_blocks(inode->i_sb, num_clusters);
+		*ret_count -= v_blkno & (u64)(bpc - 1);
 	}
-}
-
-static void __ocfs2_extent_map_drop_cleanup(struct rb_node *free_head)
-{
-	struct rb_node *node;
-	struct ocfs2_extent_map_entry *ent;
-
-	while (free_head) {
-		node = free_head;
-		free_head = node->rb_right;
 
-		ent = rb_entry(node, struct ocfs2_extent_map_entry,
-			       e_node);
-		kmem_cache_free(ocfs2_em_ent_cachep, ent);
-	}
-}
-
-/*
- * Remove all entries past new_clusters, inclusive of an entry that
- * contains new_clusters.  This is effectively a cache forget.
- *
- * If you want to also clip the last extent by some number of clusters,
- * you need to call ocfs2_extent_map_trunc().
- * This code does not check or modify ip_clusters.
- */
-int ocfs2_extent_map_drop(struct inode *inode, u32 new_clusters)
-{
-	struct rb_node *free_head = NULL;
-	struct ocfs2_extent_map *em = &OCFS2_I(inode)->ip_map;
-	struct ocfs2_extent_map_entry *ent;
-
-	spin_lock(&OCFS2_I(inode)->ip_lock);
-
-	__ocfs2_extent_map_drop(inode, new_clusters, &free_head, &ent);
-
-	if (ent) {
-		rb_erase(&ent->e_node, &em->em_extents);
-		ent->e_node.rb_right = free_head;
-		free_head = &ent->e_node;
-	}
-
-	spin_unlock(&OCFS2_I(inode)->ip_lock);
-
-	if (free_head)
-		__ocfs2_extent_map_drop_cleanup(free_head);
-
-	return 0;
-}
-
-/*
- * Remove all entries past new_clusters and also clip any extent
- * straddling new_clusters, if there is one.  This does not check
- * or modify ip_clusters
- */
-int ocfs2_extent_map_trunc(struct inode *inode, u32 new_clusters)
-{
-	struct rb_node *free_head = NULL;
-	struct ocfs2_extent_map_entry *ent = NULL;
-
-	spin_lock(&OCFS2_I(inode)->ip_lock);
-
-	__ocfs2_extent_map_drop(inode, new_clusters, &free_head, &ent);
-
-	if (ent)
-		ent->e_rec.e_clusters = cpu_to_le32(new_clusters -
-					       le32_to_cpu(ent->e_rec.e_cpos));
-
-	OCFS2_I(inode)->ip_map.em_clusters = new_clusters;
-
-	spin_unlock(&OCFS2_I(inode)->ip_lock);
-
-	if (free_head)
-		__ocfs2_extent_map_drop_cleanup(free_head);
-
-	return 0;
-}
-
-int __init init_ocfs2_extent_maps(void)
-{
-	ocfs2_em_ent_cachep =
-		kmem_cache_create("ocfs2_em_ent",
-				  sizeof(struct ocfs2_extent_map_entry),
-				  0, SLAB_HWCACHE_ALIGN, NULL, NULL);
-	if (!ocfs2_em_ent_cachep)
-		return -ENOMEM;
-
-	return 0;
-}
-
-void exit_ocfs2_extent_maps(void)
-{
-	kmem_cache_destroy(ocfs2_em_ent_cachep);
+out:
+	return ret;
 }